The field of backrests has been the subject of developmental efforts for many years. This is due largely to the fact that back pain and back disorders afflict a major segment of the population.
The human spinal column is normally formed with an elongated S-shape which may vary both as to configuration and dimensions from one individual to another. For a number of reasons such as bad posture, poor sitting habits, or poor physical condition, the natural elongated S-shape of the spinal column may become distorted. When this occurs, abnormal concentrations of pressure occur on the vertebrae and the intervertebral discs. This, in turn, causes pressure on the nerves in the spinal cord frequently resulting in severe back pain, neck pain, fatigue and headaches. A well constructed backrest, properly adjusted, tends to restore the spinal S-curve to proper configuration and thereby relieves or avoids the uneven pressures which cause troublesome pain and fatigue.
The following prior art patents disclose a variety of backrests, some of which are portable and others of which are built into chairs or vehicle seats: U.S. Pat. Nos. 2,756,809--Endresen; 2,843,195--Barvaeus; 2,894,565--Conner; 3,642,319--Berchicci; 3,663,055--Gale; 3,762,769--Poschl; 3,990,742--Glass et al.; and 4,350,338--Weiner.